Oligosaccharides are sugars containing a small number of simple sugars (monosaccharaides) which are partly digested by humans. The undigested component is fermented by intestinal bacteria. Oligosaccharides increase good gut bacteria and decrease the harmful ones. Oligosaccharides are found in animals in the plasma cell membranes. Their role is cell-to-cell recognition. (1)
Fructo-oligosaccharides (FOS) consist of short chain fructose molecules and are found in vegetables.
Galacto-oligosaccharides (GOS) consist of short chains of galactose molecules.